Clutch system

ABSTRACT

A clutch system may include in certain embodiments a clutch body attached to a drive member such as a drive pulley, wherein the clutch body may be removed from the drive member without disassembling the clutch body. In various embodiments, the clutch body may include two clutch plates which enclose a spring-loaded pneumatic reciprocating assembly that in operation causes the plates to selectively separate and engage one another. In certain embodiments, the clutch body may be readily attached to a associated drive pulley in a single step by installation of a single set of fasteners.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation-in-part of U.S. application Ser. No.10/970,356 filed on Oct. 21, 2004 and entitled “Clutch System,” theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

This document relates to a rotational control apparatus, and certainembodiments relate more particularly to a clutch apparatus.

BACKGROUND

Vehicle transmission systems, cooling systems, and braking systems oftenuse clutches or like devices to selectively transmit rotational forcesfrom a drive shaft to an output member. Conventional clutch devicesinclude an opposing pair of engagement surfaces that can be compelledtoward or away from one another using an electrical, mechanical,pneumatic, or hydraulic actuation system. In general, the actuationsystem causes some relative axial shifting within the clutch device.Such axial movement is used engage (or disengage) the opposingengagement surfaces, which rotationally interconnects (or rotationallydisconnects) the drive shaft and the output member.

In clutch devices using pneumatic or hydraulic actuated systems, apiston may be acted upon by a set of springs to bias the piston towardone of the engaged or disengaged positions. Fluid pressure may act uponthe piston, in a direction opposite to that of the spring force, tocause the piston portion to be axially shifted. Such axial movement isused engage (or disengage) the opposing engagement surfaces, thusselectively controlling the rotation between the drive shaft and theoutput member.

Clutch devices may require repair or replacement if the engagementsurfaces have worn beyond their useful life or if a component is notproperly functioning. For instance, seals and clutch engagement surfacesmay wear over time and require replacement.

The design of the clutch device can have a significant effect on thetime and cost of repair or replacement of component parts. If a clutchdevice has multiple pieces that must be disassembled before the clutchdevice can be removed from the drive shaft, the labor costs associatedwith the repair or replacement of the clutch device may increase. Inaddition, if a clutch device includes components that are spring biased,extra tooling may be required to clamp those components in place asclutch device is disassembled or removed.

The location and number of seals such as O-rings in the clutch devicemay also affect the time and cost associated with repairing or replacingclutch devices. If a seal fails and starts to leak, the time required tolocate which particular seal is broken may increase if the clutch devicehas a larger number of seals. Furthermore, the location of the seals mayaffect the likelihood of contaminants entering the fluid space. If aseal is disposed between two surfaces that move both axially androtationally relative to one another, the seal may be more susceptibleto leakage.

The longevity of the clutch device, and thus the repair interval, may beincreased by reducing wear factors such as vibration. Clutch designsbuilt with more liberal tolerances and clutch designs that allow greaterdegrees of inter-part vibration may have a shorter useful life.

SUMMARY

A clutch system may include in certain embodiments a clutch bodyattached to a drive member such as a drive pulley, wherein the clutchbody may be removed from the drive member without disassembling theclutch body. In various embodiments, the clutch body may include twoclutch plates which enclose a spring-loaded pneumatic reciprocatingassembly that in operation causes the plates to selectively separate andengage one another. In certain embodiments, the clutch body may bereadily attached to a associated drive pulley in a single step byinstallation of a single set of fasteners.

In some embodiments, a rotation control apparatus may include a clutchmember removably mounted to a drive pulley. The clutch member may have ahub portion and a piston portion. The hub portion may be selectivelymovable in a rotational direction relative to the drive pulley andsubstantially stationary in an axial direction relative to the drivepulley. The piston portion may be selectively movable in the axialdirection relative to the hub portion and substantially stationary inthe rotational direction relative to the hub portion. The clutch membermay be removable from the drive pulley while the hub portion remainsassembled with the piston portion.

In another embodiment, a rotational control apparatus includes a drivemember rotatably mounted on a support shaft. The drive member may have afirst engagement surface. A clutch member may be removably mounted tothe drive member. The clutch member may comprise a piston portionassembled with a hub portion. The piston portion may be selectivelymovable in an axial direction relative to the hub portion andsubstantially stationary in a rotational direction relative. The pistonportion may have a second engagement surface to selectively contact thefirst engagement surface. The clutch member may further include achannel in fluid communication with the piston portion, and a biasingmember to urge the second engagement surface against the firstengagement surface. The clutch member may be removable from the drivemember while the hub portion remains assembled with the piston portion.

In some embodiments, a clutch member may include an engagement surfacethat at least partially extends in a nonradial direction. For example,the clutch member may include a frusto-conical engagement surface toselectively interface with clutch material. Particular embodiments mayinclude a clutch device for removably mounting to a drive member. Theclutch device may include a frusto-conical clutch ring, which may havean increasingly larger radius as the engagement surface extends away thedriver member when the clutch device is mounted to the drive member.

These and other embodiments may be configured to provide one or more ofthe following advantages. First, the clutch member may be readilyremoved from the drive member upon removal of a single set of fasteners.Second, the clutch member may have a self-contained configuration thateliminates the need for additional clamps or tooling when removing theclutch member from the drive member. Third, the clutch member may have areduced number of seals and leakage paths; thus reducing the number ofseals along the periphery of the fluid-receiving chamber. Fourth, theseal member along the periphery of the fluid-receiving chamber may notrotate relative to an adjacent part, which may in turn improve sealquality and reduce the likelihood of contamination in the fluid system.Fifth, the clutch member may have a fluid-receiving chamber that iswholly within the removable clutch member, which may also reduce thelikelihood of contamination in the fluid system. Sixth, a splineconnection in the clutch member may reduce vibration between internalcomponents of the clutch member. Seventh, the clutch member may use asingle spring to urge the piston portion toward an engaged (ordisengaged) position, which may simplify the assembly process duringmanufacture and repair. Some or all of these and other advantages may beprovided by the clutch systems described herein.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded cross-sectional view of a rotational controlapparatus in accordance with certain embodiments of the invention.

FIG. 2 is another exploded cross-sectional view of a rotational controlapparatus of FIG. 1.

FIG. 3 is a cross-sectional side view of the rotational controlapparatus FIG. 1.

FIG. 4 is another cross-sectional side view of the rotational controlapparatus of FIG. 1.

FIG. 5 is an exploded cross-sectional view of a rotational controlapparatus in accordance with certain embodiments of the invention.

FIG. 6 is a cross-sectional side view of the rotational controlapparatus FIG. 5.

FIG. 7 is another cross-sectional side view of the rotational controlapparatus of FIG. 5.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

A number of embodiments of the invention include a rotational controlapparatus that provides simplified repair or replacement. A rotationcontrol apparatus may include a clutch member that is removably mountedto a drive member. In some embodiments, the clutch member may be removedfrom the drive member without disassembly of the clutch member'scomponent parts.

Referring to FIGS. 1-2, a drive member 100 is rotatably coupled to asupport member 115 by one or more bearings 120. A nut or collar device116 is secured to the support member 115 and is abutted to the bearing120 so that the bearings 120 remain substantially fixed in the axialdirection relative to the support member 115. The drive member 100receives one or more drive inputs, such as belts, chains, gears or thelike, to force the drive member 100 to rotate in a particular directionabout an axis 105. In this embodiment, the support member 115 is asubstantially stationary shaft, and the drive member 100 is illustratedas a drive pulley that includes an input portion 102. Rotational powerfrom a motor or the like may be transmitted through one or more driveinputs (not shown in FIGS. 1-2) to the input portion 102, thus causingthe drive pulley 100 to rotate about the central axis 105 of the supportshaft 115.

A fluid supply input 150 extends into the support member 115 forconnection to a fluid supply reservoir (not shown in FIGS. 1-2). Asupply channel 152 extends from the fluid supply input 150 in asubstantially axial direction along the central axis 105. In thisembodiment, the supply channel 152 extends through a cylindrical outlet160, which has a mating end 162 to mate with a face seal 260 of theclutch member 200. The outlet 160 may also include a spacer 164 thatfits into a shoulder 117 of the support member 115, thereby aligning theoutlet 160 with the central axis 105.

Still referring to FIGS. 1-2, the outlet 160 has an insert end 161 thatis fit into a biasing member 163. The biasing member 163 of the outlet160 is fit into an axial cavity 116 of the support member 115. Thebiasing member 163 may be a spring or block of elastic material thatbiases the mating end 162 in a substantially axial direction toward theface seal 260. As such, when the clutch member 200 is mounted to thedrive member 100 (see, for example, FIG. 3), the mating end 162 ispressed against the face seal 260 to form a mechanical seal.Accordingly, the fluid may be transmitted from the fluid supply input150 through the outlet 160 and the face seal 260 to the fluid-receivingchamber 264 of the clutch member 200. In some embodiments, the matingend 162, the face seal 260, or both may comprise metals, polymers, orcomposite materials that can substantially maintain the mechanical sealtherebetween while the clutch member 200 is selectively rotated relativeto the support member 115. In one example, the mating end 162 and theface seal 260 comprise a hardened, polished steel material. Thisconfiguration of the mechanical seal between the mating end 162 and theface seal 260 may eliminate the need for a cap member that is fit overthe mating end 162 and extends to the inner circumference of the drivepulley 100 so as to seal the radial area inside the drive pulley 100 andretain a face seal 260.

The fluid transmitted to the fluid-receiving chamber 264 of the clutchmember 200 may be any suitable liquid or gas, as described in moredetail below. Such fluids may be received, for example, from a pneumaticair supply system or a hydraulic oil supply system.

Referring more closely to FIG. 1, the clutch member 200 is removablymounted to the drive pulley 100. A fluid channel 262 extending axiallythrough the face seal 260 is substantially axially aligned with thecentral axis 105. In this embodiment, the clutch member 200 is removablymounted to the drive pulley 100 using bolts 110 that screw into threadedcavities 112 in the drive pulley 112. Alternatively, clamps may be usedto removably couple the clutch member 200 to the drive member 100.

Such a configuration of the clutch member 200 may permit the clutchmember 200 to be readily removed from the drive pulley 100. The clutchmember 200 may be removed and/or replaced in a single operation byremoving a single set of bolts 110. This configuration may obviate theneed to disassemble parts of the clutch member 200 during a replacementor repair operation. Moreover, the clutch member 200 in certainconfigurations may lessens or eliminates the need for additional clampsor tooling when removing the clutch member 200 from the drive member100, as described in more detail below. Accordingly, the time and costsassociated with the repair or replacement of the clutch member 200 maybe significantly reduced.

Referring again to FIGS. 1-2, the clutch member 200 includes a pistonportion 220 that is movably assembled with a hub portion 240. The pistonportion 220 is movable in an axial direction relative to the hub portion240 and is substantially stationary in a rotation direction relative tothe hub portion 240. In this embodiment, the motion of the pistonportion 220 relative to the hub portion 240 is accomplished by way of aspline connection. The piston portion 220 includes a first spline member224 that is substantially mated with a second spline member 244 of thehub portion 240. The splines 226 of the first spline member 224 arecomplimentary to the splines 246 of the second spline member 244 suchthat the spline members 224 and 244 are slidable relative to one anotherin an axial direction and are substantially stationary relative to oneanother in a rotational direction. In other embodiments, the motion ofthe piston portion 220 relative to the hub portion 240 may beaccomplished using one or more bushings that permit relative axialmovement and anti-rotation dowels that substantially prevent relativerotation between the piston portion 220 and the hub 240.

In the embodiment depicted in FIGS. 1-2, the piston portion 220 includesan output member 222, the first spline member 224, and a spring-engagingmember 226. The spring-engaging member 226 has a radially extendingsurface 227 that abuts with a spring 280. The spring-engaging member 226is fixedly coupled to the output member 222, for example, by bolts 228screwed into threaded cavities 223 in the output member 223. The firstspline member 224 is fixedly coupled to an output member 222, forexample, by threads on an external surface 225 of the first splinemember 224 that are mated into a threaded cavity 221 of the outputmember 222. Alternatively, the first spline member 224 may be fixedlycoupled to an output member 222, for example, by bolts screwed intothreaded cavities in the output member 222. The output member 222includes studs 230 that are configured to receive an output device, suchas fan blades (not shown in FIGS. 1-2). Accordingly, the clutch member200 may engage the drive pulley 100 so that the output member 222rotates with the drive pulley 200 to spin the fan blades. In suchembodiments, the piston portion 220 of the clutch member 200 may have adual function to selectively engage the drive pulley 100 and to act asthe output for the rotational motion. The studs 230 may be mounted intocavities 231 in the output member 222. In the presently preferredembodiment, the cavities 231 do not extend completely through the outputmember 222, thereby obviating the need for additional seals between thestuds 230 and the fluid-receiving chamber 264. In other embodiments, thestuds 230 may be threaded bolts that are inserted through threadedapertures in the output member 222 and extend forward of the outputmember 222.

Still referring to FIGS. 1-2, the hub portion 240 includes a hub 242 andthe second spline member 244. The second spline member 244 is fixedlycoupled to the hub 242, for example, by threads on an external surface245 of the second spline member 244 that are mated into a threadedcavity 243 of the hub 242. Alternatively, the second spline member 244may be fixedly coupled to the hub 242, for example, by bolts screwedinto threaded cavities in the hub 242. The hub 242 includes a cavity 248configured to receive at least a portion of the face seal 260, and thefluid channel 262 extends axially along the central axis 105 throughboth the hub 242 and the second spline member 244. The face seal 260 mayinclude threads on an external surface 261 that mate with the cavity 248of the hub 242. In an alternative embodiment, the threaded cavity 243may extend completely through the hub 242 such that the second splinemember 244 mates with the face seal 260. In such an embodiment, the faceseal 260 may mate with a cavity in the second spline member 244 similarto the cavity 248 in the hub 242.

At least one bearing 270 is disposed between the hub 242 and a fixedplate 275. The fixed plate 275 is mounted to the drive pulley 100 usingthe bolts 110 that are positioned through apertures 276 and screwed intocavities 112. As such, the fixed plate 275 is secured to the drivepulley 100 and rotates along with the drive pulley. The bearing 270permits the hub portion 240 (including the hub 242) to rotateindependently of the fixed plate 275 and the drive pulley 100. In thisembodiment, the bearing 270 is disposed along an outer circumferentialsurface 241 of the hub 242. The bearing 270 may be secured to the hub242 and the fixed plate 275 using any number of securing means, such ascollar devices, locking nuts, locking rings, tongue and groovearrangements, or the like. In this embodiment, the bearing 270 issecured to the hub 242 using a locking nut 271 so that the bearing 270remains substantially stationary relative to the hub 242 in the axialdirection. The bearing 270 is secured to the fixed plate 275 using alocking ring 271 such that the bearing 270 remains substantiallystationary relative to the fixed plate 275 in the axial direction. Assuch, the hub portion 240 may rotate independently of the fixed plate275 and drive pulley 100, but the hub portion 240 remains substantiallystationary in the axial direction relative to the fixed plate 275 anddrive pulley 100.

Still referring to FIGS. 1-2, the hub 242 includes a spring-engagingsurface 247 that abuts with the spring 280. In this embodiment, thespring 280 is a single, coiled spring that has an inner and outerdiameter to fit securely within the spring-engaging member 226 of thepiston portion 220. Using only a single spring may simplify assembly anddisassembly of the clutch member 200 during manufacture or repair.Because only one spring must be placed in the spring-engaging member226, less time is required to properly align the spring 280 duringassembly. Alternatively, other embodiments may use a more complexarrangement having a greater number of smaller springs that arepositioned adjacent one another within the spring-engaging member 226 ofthe piston portion 220.

When the clutch member 200 is assembled as shown in FIG. 1, the spring280 is compressed between the spring-engaging surface 227 of the pistonportion 220 and the spring engaging surface 247 of the hub portion 240.Such an arrangement urges the piston portion 220 in an axial directiontoward the drive pulley 100. Thus, in this embodiment, the spring 280biases the piston portion 220 such that an engagement surface 237 of thepiston portion 220 is urged against a clutch material 277, which ismounted to the drive pulley 100 using the bolts 110. When the engagementsurface 237 presses against the clutch material 277, the clutch member200 engages the drive pulley 100, and the piston portion 220 and the hubportion 240 rotate with the drive pulley 100.

Still referring to FIGS. 1-2, the clutch member 200 may disengage thedrive pulley 100 when fluid is introduced into the chamber 264 undersufficient pressure to axially shift the piston portion 220 relative tothe hub portion 240. When the engagement surface 237 is shifted awayfrom the clutch material 277 (see, for example, FIG. 4), the pistonportion 220 and the hub portion 240 are no longer driven by the rotationof the drive pulley 100 and are free to independently rotate (or stoprotating) via the bearing connection 270. As previously described, fluidmay enter the chamber 264 through the fluid channel 262. In thisembodiment, the fluid-receiving chamber 264 is at least partiallydefined by the space between the output member 222 and the hub 242. Thefluid may pass through small gaps in the spline connection between thefirst spline member 224 and the second spline member 244. When apredetermined amount of fluid pressure has built up in the chamber 264,the output member 222 is forced in an axial forward direction away fromthe drive pulley 100, thus overcoming the bias of the spring 280 to urgethe piston portion 220 toward the drive pulley 100.

Still referring to FIGS. 1-2, the fluid-receiving chamber 264 isdisposed internally in the clutch member 200. In this embodiment, thefluid in the chamber 264 may have only one possible leak path, which isalong the circumferential surface 249 of the hub 242. A seal 290 isdisposed along the periphery of the leak path between thecircumferential surface 249 of the hub 242 and the output member 220.The seal 290 is positioned as such to prevent fluid leakage through theleak path. Thus, a fluid leak may be quickly detected and repaired bychecking the seal 290 at the circumferential surface 249 and by checkingthe mechanical seal at the face seal 260. By reducing the number ofseals in the clutch member design, the time and cost associated withdetecting which seal is faulty may be significantly reduced.

In this embodiment, the seal 290 for the fluid-receiving chamber 264 isinternal to the clutch member 220 and is disposed between two surfacesthat do not rotate relative to one another about the central axis 105.As previously described, the piston portion 220 may shift in the axialdirection relative to the hub portion 240, so the seal may endure asliding motion between the circumferential surface 249 and the outputmember 222. The piston portion 220 remains substantially stationaryrelative to the hub portion 240 in the rotational direction, so the seal290 does not endure a rotational motion. When the seal 290 is internalto the clutch member 200 and is limited to such minimal sliding motion,the possibility of contaminants entering the chamber 264 through theseal 290 may be significantly reduced. Such a reduction is contaminationmay increase the longevity the clutch member 200 and may reduce the needfor repair or replacement.

Referring to FIGS. 1-2, a wiper seal 291 may also be disposed betweenthe circumferential surface 249 of the hub portion 240 and the outputmember 222 of the piston portion 220. In this embodiment, the wiper 291may slide in an axial direction when the piston portion 220 shiftsrelative to the hub portion 240. The wiper 291 is positioned against thecircumferential surface 249 so as to prevent or limit any contaminantsthat may pass into the fluid-receiving chamber. The wiper 291, the seal290, or both may comprise a material that is suitable to endure thesliding motion while limiting the flow of fluid or contaminants. Suchsuitable materials may include polymers, rubber materials, compositematerials, or the like. Depending on the manufacturing tolerances of thepiston portion 220 and the hub portion 240, a guide band (not shown inFIGS. 1-2) may be disposed between the circumferential surface 249 andthe output member 222 to prevent excess metal-on-metal contact betweenthe circumferential surface 249 and the output member 222. If such aguide band is implemented, the guide band is preferably disposed betweenthe seal 290 and the wiper 291.

Referring more specifically now to FIG. 1, the clutch member 200 mayhave a self-contained construction such that the components of clutchmember 200 (e.g., the piston portion 220, the hub portion 240, thespring 280, and so forth) remain in an assembled state even after theclutch member is removed from the drive pulley 100. In the embodimentshown in FIG. 1, the clutch member 200 may be removed from the drivepulley 100 by removing the bolts 110 from the mounting cavities 112.Removing these bolts 110, however, does not permit the internal springto move the components of the clutch member 200 apart from another andthereby cause disassembly of the clutch member 200 (e.g., the spring 280is not be free to unexpectedly expand and separate the components when aworker attempts to remove the clutch member 200 from the drive pulley100). The locking nut 272, locking ring 271, and other such devices maybe subsequently removed to disassemble the clutch member 200 at theappropriate time. Accordingly, the clutch member 200 may be removed fromthe drive pulley 100 without the use of clamps or extra tooling toretain the clutch member 200 in its assembled position.

In operation, the clutch member 200 may selectively engage the drivemember 100 so that the rotation of the output member 222 is controlled.As previously described, the depicted embodiment of the clutch member200 may disengage the drive pulley 100 when fluid is introduced into thechamber 264 under sufficient pressure to axially shift the pistonportion 220 relative to the hub portion 240. When the engagement surface237 is shifted away from the clutch material 277, the piston portion 220and the hub portion 240 are no longer driven by the rotation of thedrive pulley 100 and are free to independently rotate (or stop rotating)via the bearing connection 270.

Referring now to FIG. 3, the clutch member 200 is mounted to the drivepulley 100 and the piston portion 220 is shown in an engaged position.In this embodiment, the spring 280 is disposed between the hub portion240 and the piston portion 220 such that the spring 280 urges the pistonportion 220 in a rearward axial direction toward the drive pulley 100.The engagement surface 237 of the piston portion 220 is pressed againstthe clutch material 277, which is mounted to the drive pulley 100. Theengagement surface 237 is urged against the clutch material 277 withsufficient force so that the piston portion 220 rotates along with theclutch material 277, which is mounted to the drive pulley 100. As such,the output member 222 of the piston portion 220 rotates substantiallysynchronously with the rotation of the drive pulley 100 about thecentral axis 105. When the piston portion 220 is in the engagedposition, the output device (such as a fan) that is mounted to the studs230 of the output member 222 also rotates with the drive pulley 100.Although the hub portion 240 is not directly engaged with the drivepulley 100 or the clutch material 277, the hub portion 240 rotates withthe piston portion 220 due to the spline connection between first andsecond spline members 224 and 244. Such a configuration limits the wearon the seal 290 because the seal 290 does not endure rotational motionbetween the hub 242 and the output member 222.

Referring now to FIG. 4, the piston portion 220 is shifted forward inthe axial direction away from the drive pulley 100 such that the pistonis in a disengaged position. In this embodiment, the engagement surface237 of the piston portion 220 is spaced from the clutch material 277 byan offset 300. This offset 300 causes the piston portion 220 todisengage with the clutch material 277 so that the rotational motionfrom the drive pulley 100 is not transferred to the output member 222.When the piston portion 220 is in the disengaged position, the pistonportion 220 and hub portion 240 are free to rotate independently fromthe drive pulley 100 due to the bearing connection 270. Accordingly, thepiston portion 220 and the hub portion 240 may stop rotating even thoughthe drive pulley 100 continues to rotate.

Referring to FIGS. 3-4, the offset 300 of the piston portion 220 occurswhen a fluid under sufficient pressure is received in the chamber 264.If force from the fluid pressure in the chamber 264 is sufficient toovercome the force of the spring 280, the output member 220 (and theentire piston portion 220) is shifted forward in the axial direction. Insome embodiments, the fluid pressure that is required to overcome thespring force may be approximately predetermined from the springconstant, the desired offset 300, the dimensions of the chamber 264, andother such factors. As previously described, the fluid supply input 150receives the fluid from the reservoir (not shown in FIGS. 3-4). Thefluid passes through the fluid supply channel 152, through the outlet160 and the face seal 260, through the fluid channel 262, and into thechamber 264. The mechanical seal at the face seal 260 assures that thefluid properly reaches the chamber 264, and when the fluid is in thechamber 264, the seal 290 prevents the fluid from passing through thepotential leak path along the circumferential surface 249 (FIG. 2).

In this embodiment of the clutch member 200 depicted in FIGS. 3-4, thepiston portion 220 serves as both the portion that engages the drivepulley 100 (via the clutch material 277) and the portion that receivesan output device (such as a fan). The output device mounted to the studs230 of the piston portion 220 may also be shifted in the axial directionas the piston portion 220 is shifted, but the offset 300 in the axialdirection may be relatively small such that this shifting motion haslittle or no impact on the output device. Similarly, the offset 300 inthe axial direction may be relatively small such that the shiftingmotion of the output member 222 relative to the hub 242 has little or noimpact on the longevity and performance of the seal 190 and the wiper191. It should be understood that the displacement between the clutchmaterial 277 and the engagement surface 237 may change slightly as theclutch material 277 is worn away through normal use.

In another embodiment of the invention, the drive member 100 may have aconfiguration other than a drive pulley shown in FIGS. 1-4. For example,the drive member 100 may be a shaft or gear that is powered by a motor.In such embodiments, the clutch member 200 may have a mountingconfiguration to removably attach to the shaft or gear or may have anadapter member connected therebetween.

In other embodiments, the output member 222 of the clutch member 200 maybe configured to receive an output device other than fan blades. Forexample, the output member 222 may be configured to connect with othercomponents that are to be selectively rotated, such as output shafts,gears, brake systems, and the like.

In yet another embodiment, the spring 280 that biases the piston portion220 in an axial direction is not limited to a single, coiled springshown in FIGS. 1-4. Rather, the spring 280 can be any biasing memberthat can urge the piston portion 220 in the axial direction. A suitablebiasing member may comprise one or more coil springs, leaf springs, gassprings, solid materials having appropriate elasticity properties, orthe like.

Furthermore, some embodiments of the invention may include a clutchmember configuration such that spring 280 urges the piston portion 220to disengaged position (where the engagement surface 237 is offset fromthe clutch material 277). In such embodiments, the chamber 264 may beconfigured such that fluid pressure therein causes the piston portion220 to shift toward engaged position (where the engagement surface 237is pressed against the clutch material 277).

In other embodiments, the clutch material 277 may be integral with thefixed plate 275 or the drive member 100. In these embodiments, theengagement surface 237 of the piston portion 220 would engage with anopposing surface on the fixed plate 275 of the drive member 100.

In another embodiment, the clutch material may be mounted to the pistonportion 220 such that the clutch material selectively engages with anopposing surface (e.g., the clutch material 277, the fixed plate 275 orthe drive member 100). In such an embodiment, an engagement surface onthe clutch material would contact the opposing surface.

Referring to FIGS. 5-7, some embodiments of a clutch member 600 mayinclude an engagement surface 637 that at least partially extends in anonradial direction. For example, a clutch member 600 may include afrusto-conical interface between the clutch material and the engagementsurface. In this embodiment, a frusto-conical clutch ring 677 mayselectively engage a frusto-conical surface 637. The frusto-conicalengagement surface 637 has a first radius 639 and a second radius 641,with the first radius 639 being axially closer to drive member 500. Inthis embodiment, the first radius 639 is smaller than the second radius641. As such, the frusto-conical clutch ring 677 may have anincreasingly larger radius as the engagement surface extends away fromthe drive member 500 when the clutch member 600 is mounted to the drivemember 500.

Similar to some previously described embodiments, the drive member 500can be rotatably coupled to a support member 515 by one or more bearings520. The drive member 500 receives one or more drive inputs, such asbelts, chains, gears or the like, to force the drive member 500 torotate in a particular direction about an axis 505. In this embodiment,the support member 515 is a substantially stationary shaft, and thedrive member 500 is illustrated as a drive pulley that includes an inputportion 502.

A fluid supply input 550 extends into the support member 515 forconnection to a fluid supply reservoir (not shown in FIGS. 5-7). Asupply channel 552 may extend from the fluid supply input 550 in asubstantially axial direction along the central axis 505. In thisembodiment, the supply channel 552 mates with a face seal 660 of theclutch member 600. When the clutch member 600 is mounted to the drivemember 500 (see, for example, FIG. 6), the supply channel 552 is pressedagainst the face seal 660 to form a mechanical seal. Accordingly, thefluid may be transmitted from the fluid supply input 550, through afluid channel 662, and to the fluid-receiving chamber 664 of the clutchmember 600.

Referring to FIG. 5, the clutch member 600 may be removably mounted tothe drive member 500. In this embodiment, the clutch member 600 isremovably mounted to the drive member 500 using bolts 510 that screwinto threaded cavities 512 in the drive member 500. In anotherembodiment, clamps may be used to removably couple the clutch member 600to the drive member 500.

Such a configuration of the clutch member 600 may permit the clutchmember 600 to be readily removed from the drive member 500. The clutchmember 600 may be removed and/or replaced in a single operation byremoving a single set of bolts 510. Similar to some previously describedembodiments, this configuration may obviate the need to disassembleparts of the clutch member 600 during a replacement or repair operation.

Still referring to FIG. 5, the clutch member 600 includes a pistonportion 620 that is movably assembled with a hub portion 640. The pistonportion 620 is movable in an axial direction relative to the hub portion640 and is substantially stationary in a rotation direction relative tothe hub portion 640. Similar to some previously described embodiments,the motion of the piston portion 620 relative to the hub portion 640 maybe accomplished by way of a spline connection. The piston portion 620includes a first spline member 624 that may be substantially mated witha second spline member 644 of the hub portion 640.

The piston portion 620 includes studs 630 that are configured to receivean output device, such as fan blades (not shown in FIGS. 5-7).Accordingly, the clutch member 600 may engage the drive member 500 sothat the piston portion 620 rotates with the drive member 500 to spinthe fan blades. In such embodiments, the piston portion 620 of theclutch member 600 may have a dual function to selectively engage thedrive member 500 and to act as the output for the rotational motion.

In this embodiment, the hub portion 640 includes a hub 642 and thesecond spline member 644. The hub 642 includes a cavity 648 configuredto receive at least a portion of the face seal 660, and the fluidchannel 662 extends axially along the central axis 505 through both thehub 642 and the second spline member 644. Similar to some previouslydescribed embodiments, a seal 690 may be disposed along the periphery ofthe leak path between hub 642 and the output member 620. The seal 690 ispositioned as such to prevent fluid leakage through the leak path. Thus,a fluid leak may be quickly detected and repaired by checking the seal690 at the circumferential surface and by checking the mechanical sealat the face seal 660. By reducing the number of seals in the clutchmember design, the time and cost associated with detecting which seal isfaulty may be significantly reduced. Similar to some previouslydescribed embodiments, the clutch member 600 may optionally include awiper seal 691. The wiper seal 691 may prevent migration of contaminantstoward the seal 690 that actually borders the fluid receiving chamber664.

At least one bearing 670 may be disposed between the hub 642 and a fixedplate 675. The fixed plate 675 may be removably mounted to the drivemember 500 using the bolts 510 that are positioned through apertures 676and screwed into cavities 512. As such, the fixed plate 675 can besecured to the drive member 500 and rotates along with the drive member500. The bearing 670 permits the hub 642 to rotate independently of thefixed plate 675 and independently of the drive member 500. In thisembodiment, the bearing 670 may be secured to the hub 642 using alocking nut 672 so that the bearing 670 remains substantially stationaryrelative to the hub 642 in the axial direction. The bearing 670 may besecured to the fixed plate 675 using a locking ring 671 such that thebearing 670 remains substantially stationary relative to the fixed plate675 in the axial direction. As such, the hub 642 may rotateindependently of the fixed plate 675 and independently of the drivemember 500, but the hub 642 remains substantially stationary in theaxial direction relative to the fixed plate 675 and drive member 500.

Still referring to FIG. 5, the hub 642 includes a spring-engagingsurface 647 that abuts with a biasing member, such as a spring 680. Inthis embodiment, the spring 680 is a single, coiled spring that has aninner and outer diameter to fit securely within the spring-engagingmember 626 of the piston portion 620.

When the clutch member 600 is assembled as shown in FIG. 5, the spring680 may be compressed between the spring-engaging surface 627 of thepiston portion 620 and the spring engaging surface 647 of the hub 642.Such an arrangement urges the piston portion 620 in an axial directiontoward the drive member 500. Thus, in this embodiment, the spring 680biases the piston portion 620 such that the frusto-conical clutch ring677 (mounted to the piston portion 620 in this embodiment) is urgedagainst the frusto-conical engagement surface 637 of the fixed plate675, which is mounted to the drive member 500 using the bolts 510. Whenthe frusto-conical clutch ring 677 of the piston portion 620 pressesagainst the frusto-conical engagement surface 637 of the fixed plate675, the piston portion 620 engages the fixed plate 675, and the pistonportion 620 rotates with the drive member 500. The clutch ring 677 maycomprises a metallic, ceramic or other material that is capable ofproviding frictional engagement and is capable of dissipating heatgenerated at the frictional interface. For example, some embodiments ofthe clutch ring 677 may comprise a material having a static coefficientor friction in the range of approximately 0.2 to approximately 0.6 and,in particular embodiments, may comprises a material having a staticcoefficient of friction in the range of approximately 0.4 toapproximately 0.5.

Still referring to FIG. 5, the piston portion 620 may disengage the hub642 when fluid is introduced into the chamber 664 under sufficientpressure to axially shift the piston portion 620 relative to the hubportion 640. Such an axial shift of the piston portion 620 may cause thefrusto-conical clutch ring 677 to disengage the opposing engagementsurface (e.g., the engagement surface 637 of the fixed plate 675 in thisembodiment). In such circumstances, the piston portion 620 may not bedriven by the rotation of the drive member 500 so that the pistonportion 620 is free to independently rotate (or stop rotating) due tothe bearing connection 670.

In this embodiment, the fluid-receiving chamber 664 is at leastpartially defined by the space between the output member 622 and the hub642. In some embodiments, the fluid may pass through small gaps in thespline connection between the first spline member 624 and the secondspline member 644. When a predetermined amount of fluid pressure hasbuilt up in the chamber 664, the output member 622 is forced in an axialforward direction away from the hub 642, thus overcoming the bias of thespring 680 to urge the piston portion 620 in the axial forwarddirection.

Similar to some previously described embodiments, the clutch member 600may have a self-contained construction such that the components ofclutch member 600 (e.g., the piston portion 620, the hub portion 640,the spring 680, the frusto-conical clutch ring 677, and so forth) remainin an assembled state even after the clutch member 600 is removed fromthe drive member 500. In the embodiment shown in FIG. 5, the clutchmember 600 may be removed from the drive member 500 by removing thebolts 510 from the mounting cavities 512.

Referring now to FIGS. 6-7, the clutch member 600 may be operated toselectively engage the drive member 500 so that the rotation of theoutput member 622 is controlled. As previously described, the depictedembodiment of the clutch member 600 may disengage the drive member 500when fluid is introduced into the chamber 664 under sufficient pressureto axially shift the piston portion 620 relative to the hub portion 640.When the frusto-conical clutch ring 677 is shifted away from thefrusto-conical engagement surface 637, the piston portion 620 is nolonger driven by the rotation of the drive member 500 (and the fixedplate 675) and is thereby free to independently rotate (or stoprotating) via the bearing connection 670.

As shown in FIG. 6, the clutch member 600 is mounted to the drive member500, and the piston portion 620 is in an engaged position. In thisembodiment, the spring 680 is disposed between the hub portion 640 andthe piston portion 620 such that the spring 680 urges the piston portion620 in a rearward axial direction (toward the drive member 500). Thefrusto-conical clutch ring 677 of the piston portion 620 is pressedagainst the frusto-conical engagement surface 637 of the fixed plate675, which is mounted to the drive member 500. The frusto-conical clutchring 677 is urged against frusto-conical engagement surface 637 withsufficient force so that the piston portion 620 rotates along with thefixed plate 675, which is mounted to the drive member 500. As such, theoutput member 622 of the piston portion 620 rotates substantiallysynchronously with the rotation of the drive member 500 about thecentral axis 505. When the piston portion 620 is in the engagedposition, the output device (such as a fan or fan blades) that ismounted to the studs 630 of the output member 622 also rotates with thedrive member 500. Although the hub 642 is not directly engaged with thedrive member 500 or the frusto-conical engagement surface 637 of thefixed plate 675, the hub 642 rotates with the piston portion 620 due tothe spline connection between the first and second spline members 624and 644. Such a configuration may limit the wear on the seal 690 becausethe seal 690 does not endure rotational motion between the hub 642 andthe output member 622.

Referring now to FIG. 7, the piston portion 620 may be shifted forwardin the axial direction away from the drive member 500 such that thepiston portion 620 is in a disengaged position. In this embodiment, thefrusto-conical clutch ring 677 may be mounted to the piston portion 620so it is axially shifted away from the frusto-conical engagement surface637 by an offset 700. This offset 700 causes the piston portion 620 todisengage with the fixed plate 675 so that the rotational motion fromthe drive member 500 is not transferred to the output member 622. Whenthe piston portion 620 is in the disengaged position, the piston portion620 and hub portion 640 are free to rotate independently from the drivemember 500 due to the bearing connection 670. Accordingly, the pistonportion 620 and the hub 642 may stop rotating even though the drivemember 500 and the fixed plate 675 continue to rotate. It should beunderstood that, in other embodiments, the clutch ring 677 may bemounted to the fixed plate 675, in which case the clutch ring 677 mayselectively engage a frusto-conical surface 628 of the piston portion620. In such circumstances, the piston portion 620 may be axiallyshifted to cause an offset between the clutch ring 677 and thefrusto-conical surface 628.

Referring to FIGS. 6-7, the offset 700 of the piston portion 620 mayoccur when a fluid under sufficient pressure is received in the chamber664. If force from the fluid pressure in the chamber 664 is sufficientto overcome the force of the spring 680, the output member 622 (and, inthis embodiment, the entire piston portion 620) is shifted forward inthe axial direction. In some embodiments, the fluid pressure that isrequired to overcome the spring force may be approximately predeterminedfrom the spring constant, the desired offset 700, the dimensions of thechamber 664, and other such factors. As previously described, the fluidsupply input 550 may receive the fluid, such as air, from the reservoir(not shown in FIGS. 6-7). The fluid passes through the fluid supplychannel 552, through the fluid channel 662, and into the chamber 664.The mechanical seal at the face seal 660 assures that the fluid properlyreaches the chamber 664, and when the fluid is in the chamber 664, theseal 690 may prevent the fluid from passing through a potential leakpath along the circumferential surface 649 of the hub 642.

Some embodiments of a clutch member 600 having a frusto-conicalengagement surface 637, such as those embodiments described inconnection with FIGS. 5-7, may provide substantial torque transfercapabilities between the drive member 500 and the output device. Forexample, some embodiments of the clutch member 600 may provide torqueratings of approximately 2700 in-lbs, 2800 in-lbs, 2900 in-lbs, 3000in-lbs, or more, and particular embodiments may provide torque ratingsin the range of approximately 3000 in-lbs to approximately 5000 in-lbs.As described in more detail below, the coefficient of friction of theclutch ring 577, the conical angle of the clutch ring 677, the force ofthe spring 680, and other factors affect the torque rating of the clutchmember 600.

These substantial torque transfer capabilities may be caused by a numberof factors. For example, the shape and orientation of the frusto-conicalengagement surface 637 and the frusto-conical clutch ring 677 mayprovide the clutch member 600 with a conical wedging action. Thisconical wedging action may improve the engagement friction, therebyproviding an increase in the torque transfer capabilities.

In another example, the shape and orientation of the frusto-conicalengagement surface 637 and the frusto-conical clutch ring 677 mayprovide the clutch member 600 with a reduced rotational moment ofinertia. Because some embodiments of the frusto-conical clutch ring 677do not necessarily extend as far in an outward radial direction, thepiston portion 620 may have less radial mass (in the form of metallicportions or other components extending generally in an outward directionaway from the rotational axis). As such, the overall rotational momentof inertia of the piston portion 620 may be reduced, which may increasethe torque transfer capabilities of the clutch member 600.

Torque capability testing may be conducted on clutch members 600 todetermine the torque ratings. For example, a torque capability testmethod may include mounting the clutch member 600 to a drive member 500,as shown, for example, in FIG. 6. The torque capability testing methodmay also include securing the drive member 500 in a fixed position(e.g., in a vice or a similar device), which in turn secures theposition of the engagement surface 637 (e.g., disposed on the fixedplate 675 in the depicted embodiments). In this example, a torquemeasuring device (e.g., a torque meter or the like) may be secured tothe output member 622. In accordance with this implementation of thetorque capability test method, the clutch member may be in an engagedcondition so that the frusto-conical clutch ring 677 is in frictionalcontact with the engagement surface 637. The torque measuring device maybe used to measure a torque applied to the output member 622 relative tothe drive member 500 (e.g., applying a force in an attempt to rotate theoutput member 622) and may be monitored to determine the torque levelrequired to cause slippage between the output member 622 and the drivemember 500. This implementation of the torque capability test method maybe used to determine the torque rating of the clutch member 600 (e.g.,the level of torque required to cause slippage between the output member622 and the drive member 500 when the clutch member 600 was in anengaged condition).

Certain factors of the clutch member's configuration may be affect thetorque transfer capabilities and the torque rating of the clutch member600. For example, the conical angle of the clutch ring 677 (refer, forexample, to angle A in FIG. 7) may be selected to optimize the torquerating of the clutch member 600. In some embodiments, the conical angleA may be approximately 10 degrees to approximately 60 degrees,approximately 15 degrees to approximately 45 degrees, or approximately20 to approximately 40 degrees. In the embodiment depicted in FIGS. 5-7,the conical angle A is approximately 30 degrees.

In another example of a factor that can affect the torque transfercapabilities, the material of the clutch ring 677 and/or the engagementsurface 637 may be selected to provide a particular coefficient offriction. In some embodiments, the clutch member 600 may include clutchring material having a static coefficient of friction in the range ofapproximately 0.3 to approximately 0.6, approximately 0.35 toapproximately 0.55, or approximately 0.4 to approximately 0.55. Suitablematerials for the clutch ring 677 may be provided, for example, byTrimat Ltd. of Brierley Hill, England or by Scan Pac Mfg., Inc. ofMenomonee Falls, Wis.

In a further example of a factor that can affect the torque transfercapabilities, the force of the spring 680 (or the force from the fluidpressure in the chamber 664 used to overcome the spring 680) may beselected to provide a particular compression force between the clutchring 677 and the engagement surface 637. In some embodiments, the spring680 may provide a force (to bias the clutch ring 677 and the engagementsurface 637 toward one another) of approximately 700 lbs, 800 lbs, 900lbs, 1000 lbs, 1100 lbs, 1200 lbs, 1300 lbs, 1400 lbs, 1500 lbs, orgreater. The displacement of the spring 680 may be different dependingupon the wear of the clutch ring 677, so in some embodiments, the forcefrom the spring 680 may be in the range of approximately 800 lbs toapproximately 1400 lbs. For example, the spring 680 may provide a forceof approximately 1100 lbs to approximately 1400 lbs when a substantiallyunworn clutch ring 677 is pressed against the engagement surface 637. Inthe embodiment depicted in FIGS. 5-7, the spring 680 may provide a forceof approximately 1250 lbs when a substantially unworn clutch ring 677 ispressed against the engagement surface 637. When the clutch ring 677becomes substantially worn after repeated use, the displacement of thespring 680 may be different so that the compression force provide fromthe spring is lower. For example, the spring 680 may provide a force ofapproximately 800 lbs to approximately 1100 lbs when a substantiallyworn clutch ring 677 is pressed against the engagement surface 637. Inthe embodiment depicted in FIGS. 5-7, the spring 680 may provide a forceof approximately 1000 lbs when a substantially worn clutch ring 677 ispressed against the engagement surface 637.

Accordingly, by making appropriate selections from (i) the conical angleA, (ii) the coefficient of friction at the interface between the clutchring 677 and the engagement surface 637, (iii) the force from the spring680, and (iv) other such factors, the clutch member 600 may have atorque rating of approximately 2700 in-lbs, 2800 in-lbs, 2900 in-lbs,3000 in-lbs, or more, and particular embodiments may provide torqueratings in the range of approximately 3000 in-lbs to approximately 5000in-lbs-including torque ratings in the ranges of approximately 3200in-lbs to approximately 4000 in-lbs and approximately 4000 in-lbs toapproximately 5000 in-lbs. In some embodiments of a clutch member 600having a conical angle A of approximately 30 degrees, having a clutchring 677 having a static coefficient of friction of approximately 0.4,and having a spring force of approximately 1250 lbs when the clutch ring677 is substantially unworn, the clutch member 600 may have torqueratings in the range of approximately 3200 in-lbs to approximately 4000in-lbs. For example, a clutch member 600 that had a clutch ring 677comprising Trimat MR8728 material (supplied by Trimat Ltd.) with astatic coefficient of friction of approximately 0.4, had a conical angleA of approximately 30 degrees, and had a spring force of approximately1250 lbs (when the clutch ring 677 was substantially unworn) providedtorque ratings of approximately 3540 in-lbs, 3648 in-lbs, 3780 in-lbs,3444 in-lbs, 3576 in-lbs, and 3636 in-lbs.

In other embodiments, a clutch member 600 having a clutch ring materialwith a greater static coefficient of friction (e.g., comprising Aramidmaterials supplied by either Trimat Ltd. or Scan Pac Mfg., Inc., TrimatTF100 material, or the like) may provide greater torque ratings. Forexample, some embodiments of a clutch member 600 may have a clutch ring677 with a static coefficient of friction of approximately 0.5 (e.g.,comprising Trimat TF100 material), may have a conical angle A ofapproximately 30 degrees, and may have a spring force of approximately1250 lbs when the clutch ring 677 is substantially unworn, and such aclutch member 600 may have torque ratings in the range of approximately4000 in-lbs to approximately 5000 in-lbs. Because a greater coefficientof friction may increase the frictional interface between the clutchring 677 and the engagement surface 637, some embodiments of the clutchmember 600 may have a torque rating greater than 5000 in-lbs.

Thus, some embodiments of the clutch member 600 may provide torqueratings of approximately 2700 in-lbs, 2800 in-lbs, 2900 in-lbs, 3000in-lbs, or more. Particular embodiments may provide torque ratings inthe range of approximately 3000 in-lbs to approximately 5000in-lbs—including torque ratings in the ranges of approximately 3200in-lbs to approximately 4000 in-lbs and approximately 4000 in-lbs toapproximately 5000 in-lbs.

It should be understood that the drive member 500 may have aconfiguration other than a drive pulley shown in FIGS. 5-7. For example,the drive member 500 may be a shaft or gear that is powered by a motor.In such embodiments, the clutch member 600 may have a mountingconfiguration to removably attach to the shaft or gear or may have anadapter member connected therebetween.

In other embodiments, the output member 622 of the clutch member 600 maybe configured to receive an output device other than fan blades. Forexample, the output member 622 may be configured to connect with othercomponents that are to be selectively rotated, such as output shafts,gears, brake systems, and the like.

In yet another embodiment, the spring 680 that biases the piston portion620 in an axial direction is not limited to a single, coiled springshown in FIGS. 5-7. Rather, the spring 680 can be any biasing memberthat can urge the piston portion 620 in the axial direction. A suitablebiasing member may comprise one or more coil springs, leaf springs, gassprings, solid materials having appropriate elasticity properties, orthe like.

Furthermore, some embodiments may include a clutch member configurationsuch that the spring 680 urges the piston portion 620 into thedisengaged position (where the frusto-conical engagement surface 637 isoffset from the frusto-conical clutch material 677). In suchembodiments, the chamber 664 may be configured such that fluid pressuretherein causes the piston portion 620 to shift toward engaged position(where the frusto-conical engagement surface 637 is pressed against theclutch material 677).

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.Accordingly, other embodiments are within the scope of the followingclaims.

1. A fan clutch device that is removably mountable to a drive member,the fan clutch device comprising: a hub portion selectively movable in arotational direction relative to a drive member when the fan clutchdevice is mounted to the drive member; a piston portion slidably coupledto the hub portion, the piston portion being selectively movable in anaxial direction relative to the hub portion and substantially stationaryin a rotation direction relative to the hub portion, a frusto-conicalclutch ring including an engagement surface, the frusto-conical clutchring having an increasingly larger radius as the engagement surfaceextends away the driver member when the fan clutch device is mounted tothe drive member.
 2. The fan clutch device of claim 1, wherein the hubportion from the piston portion remain coupled when the fan clutchdevice is removed from the drive member.
 3. The fan clutch device ofclaim 1, further comprising a biasing member disposed between the hubportion and the piston portion.
 4. The fan clutch device of claim 1,wherein the piston portion comprises a frusto-conical surface to contactthe clutch ring.
 5. The fan clutch device of claim 4, further comprisinga first member removably mountable to the drive member, the first memberhaving a frusto-conical surface to contact the clutch ring.
 6. The fanclutch device of claim 5, wherein the clutch ring is mounted to thefrusto-conical surface of the piston portion and the clutch ringselectively engages the frusto-conical surface of the first member aspiston portion is selectively moved in the axial direction.
 7. The fanclutch device of claim 1, further comprising a channel in fluidcommunication with a fluid-receiving space defined at least partially bysurfaces of the hub portion and the piston portion.
 8. The fan clutchdevice of claim 7, wherein the piston portion selectively moves relativeto the hub portion when a predetermined fluid pressure is applied in thefluid-receiving space.
 9. The fan clutch device of claim 1, furthercomprising an output member to couple with one or more fan blades,wherein when the clutch ring is in an engaged condition and the fanclutch device is mounted to the drive member, the torque required tocause slippage between the output member and the drive member is about3000 in-lbs to about 5000 in-lbs.
 10. A clutch apparatus, comprising: adrive member; and a clutch member removably mounted to the drive member,the clutch member having a hub portion, a piston portion, and afrusto-conical engagement surface, the hub portion being selectivelymovable in a rotational direction relative to the drive pulley andsubstantially stationary in an axial direction relative to the drivepulley, the piston portion being selectively movable in the axialdirection relative to the hub portion and substantially stationary inthe rotation direction relative to the hub portion, wherein the clutchmember is removable from the drive pulley without decoupling the hubportion from the piston portion.
 11. The apparatus of claim 10, furthercomprising a fluid-receiving space disposed at least partially withinthe clutch member, the space being defined at least partially bysurfaces of the hub portion and the piston portion.
 12. The apparatus ofclaim 10, wherein the frusto-conical engagement surface is disposed on aclutch ring, the frusto-conical engagement surface having anincreasingly larger radius as the engagement surface extends away thedriver member when the clutch member is mounted to the drive member. 13.The apparatus of claim 12, wherein the frusto-conical engagement surfaceof the clutch ring abuts an opposing frusto-conical engagement surfacecoupled to the drive pulley when in a first operative position and isoffset from the opposing frusto-conical engagement surface when in asecond operative position.
 14. The apparatus of claim 13, wherein theclutch member further comprises a biasing member to urge the pistonportion to the first operative position
 15. The apparatus of claim 14,wherein the frusto-conical engagement surface of the clutch ring isurged to the second operative position when fluid pressure is applied toa fluid-receiving space disposed at least partially within the clutchmember.
 16. The apparatus of claim 15, wherein the piston portion movesrelative to the hub portion when a predetermined fluid pressure isapplied in the fluid-receiving space.
 17. The apparatus of claim 10,wherein the clutch member has a self-contained construction such thatthe hub portion, the piston portion, and the frusto-conical engagementsurface remain coupled to one another upon removal of the clutch memberfrom the drive member.
 18. The apparatus of claim 17, wherein the clutchmember further comprises at least one locking member mounted to the hubportion such that hub portion, the piston portion, and the secondengagement surface may be decoupled from one another upon removal of theat least one locking member.
 19. The apparatus of claim 10, furthercomprising an output member to couple with one or more fan blades,wherein when the clutch ring is in an engaged condition, the torquerequired to cause slippage between the output member and the drivemember is about 3000 in-lbs to about 5000 in-lbs.
 20. A fan clutchdevice for removably mounting to a drive member, the fan clutch devicecomprising: an output member to selectively rotate with a drive memberwhen the fan clutch device is mounted to the drive member, the outputmember having one or more mounting members to receive one or more fanblades; and a clutch ring including an engagement surface to selectivelyengage an opposing surface so that, when the clutch ring engages theopposing surface and the fan clutch device is mounted to the drivemember, the output member rotates with the drive member, wherein, whenthe clutch ring engages the opposing surface and the fan clutch deviceis mounted to the drive member, the torque required to cause slippagebetween the output member and the drive member is about 3000 in-lbs orgreater.
 21. The fan clutch device of claim 20, wherein the torquerequired to cause slippage between the output member and the drivemember is in the range of about 3000 in-lbs to about 5000 in-lbs. 22.The fan clutch device of claim 21, wherein the torque required to causeslippage between the output member and the drive member is in the rangeof about 3200 in-lbs to about 4000 in-lbs.
 23. The fan clutch device ofclaim 21, wherein the torque required to cause slippage between theoutput member and the drive member is in the range of about 4000 in-lbsto about 5000 in-lbs.
 24. The fan clutch device of claim 20, wherein theclutch ring is a frusto-conical clutch ring.
 25. The fan clutch deviceof claim 24, wherein the engagement surface of the frusto-conical clutchring has an increasingly larger radius as the engagement surface extendsaway the driver member when the fan clutch device is mounted to thedrive member.
 26. The fan clutch device of claim 24, wherein thefrusto-conical clutch ring has a conical angle of about 10 degrees toabout 60 degrees.
 27. The fan clutch device of claim 26, wherein thefrusto-conical clutch ring has a conical angle of about 20 to about 40degrees.
 28. The fan clutch device of claim 20, wherein the engagementsurface of the clutch ring has a static coefficient of friction of about0.3 to about 0.6.
 29. The fan clutch device of claim 28, wherein thestatic coefficient of friction of about 0.4 to about 0.55.
 30. The fanclutch device of claim 20, further comprising a biasing member to urgethe engagement surface of the clutch ring toward the opposing surface,the biasing member providing a spring force of about 1100 lbs to about1400 lbs when the clutch ring is substantially unworn and engages theopposing surface.